Although, to my ears, it has the ring of informality, it has been around at least a century. OED has this in something, sense “2 c. Qualifying an adv. of manner. Also with adj. used for adv. in dial. and colloq. usage.”
The first entry that involves an adjective rather than an adverb is by that great recorder, George Bernard Shaw:

1898 G. B. Shaw You never can Tell in Plays Pleasant 211 Gentleman: Did you howl? The Young Lady: Oh, something awful.